Freezer apparatus

ABSTRACT

A freezer for a product includes a housing having a space therein, and an inlet and an outlet in communication with the space; a conveyor having a first side for conveying the product through the space, and a second side opposite to the first side; an agitating apparatus disposed proximate the conveyor for contacting the conveyor at select intervals to agitate the conveyor and displace the product at the first side; a first longitudinal member disposed proximate the first side of the conveyor and having at least one hole extending therethrough; and at least one circulation device disposed in the space proximate the longitudinal member for directing a cryogenic substance through the at least one hole onto the product.

BACKGROUND

The present embodiments relate to apparatus for freezing products, such as food products, with cryogenic substances.

In known individual quick frozen (IQF) freezer apparatus and processes, heat transfer in the process is limited because a driving force for convective heat transfer is employed with the use of conventional axial flow fan blades. In certain cryogen freezers, a product surface area is constantly exposed to air flow from fans which serve to accelerate the freezing rate during the process. The rate at which the product is frozen is dependent upon the heat transfer coefficient of the fans used in the freezing process. To date, only axial flow fans have been used for the heat transfer.

If a more aggressive heat transfer could be applied with impingement jets, the freezing process would be of shorter duration, thereby reducing the cost to operate the system while at the same time improving product quality because the product would be frozen more quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present embodiments, reference may be had to the following drawing figures taken in conjunction with the description of the embodiments, of which:

FIG. 1 shows a cross-sectional side view of an IQF impingement freezer convective embodiment.

FIG. 2 shows an exploded view of a portion of a cross-section of the embodiment shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a freezer apparatus embodiment is shown generally at 10 and includes a housing 12 or shell in which a space 14 or chamber is provided therein. The housing 12 includes an inlet 16 at one end and an outlet 18 at another end, the inlet and the outlet providing access to the space 14. A conveyor belt 20 is operatively associated with the housing 12, in that the conveyor belt moves from the inlet 16 through the space 14 to the outlet 18 to transport a product or products 22 through the space 14 for freezing. The product 22 may be a food product.

The conveyor belt 20 is used for individual quick frozen (IQF) product processing, i.e. the conveyor belt 20 is an IQF belt which is constructed for agitation, vibration and/or undulation as indicated by arrow 21 along that portion of the belt 20 that transports the product 22 through the space 14. The conveyor belt 20 can be selected to vibrate in a rapid manner so that the product 22 does not adhere to the belt or other of the product on the belt during the freezing process. This sort of vibrating or agitating effect of the belt exposes all surface area of the products 22 to the freezing process that occurs in the space 14. Conveyor belts that vibrate, agitate or undulate are known for freezers and examples of such are disclosed in U.S. Pat. Nos. 7,296,431, 7,827,818 and 7,810,347.

At least one fan 24 driven by a fan motor 26 is disposed such that the fan is in the space 14 for moving or propelling atmosphere in the space toward the conveyor belt 20. The conveyor belt 20 used for this embodiment would more than likely be an open mesh type of conveyor belt.

Also disposed in the space 14 is an upper impingement plate 28 which is disposed between an upper surface of the conveyor belt 20 and the at least one fan 24. The upper impingement plate 28 includes at least one and for most applications a plurality of impingement holes 30 through which the cryogen atmosphere is propelled to impact the product 22 moving along the conveyor belt 20. Each of the holes 30 may have a diameter of 6 mm to 50 mm, and are in registration with the conveyor belt 20.

It is also possible to have a lower impingement 32 disposed beneath a lower surface of the conveyor belt 20 and of a construction similar to that of the upper impingement plate 28. The lower impingement plate 32 includes at least one and for most applications a plurality of holes 34 through which the cryogen atmosphere circulated within the space 14 can pass through the holes 34 and the conveyor belt 20 for impacting the product 22. Each of the holes 34 may have a diameter of 6 mm to 50 mm, and are in registration with the conveyor belt 20. Therefore, both of the impingement plates 28,32 can be used in the space 14 so that maximum heat transfer for the products 22 can be provided by the impinging atmosphere shown by arrows 36,38 being moved through the holes 30,34, respectively, to contact the products 22. Impingement plates are known for freezers and an example of such is disclosed in U.S. Pat. No. 6,263,680. The open mesh form of conveyor belt 20 provides for the movement of the impingement jets 36,38 to pass through the conveyor belt. The impingement plates 28,32 can be supported in the space 14 as shown in FIG. 1 by being mechanically fastened to an interior surface 15 of the housing 12.

A vibrating apparatus 40 is arranged to selectively contact the conveyor belt 20 and impart a force to the belt to vibrate the belt as shown by the arrow 21 so that the products 22 are displaced on the belt. The vibrating apparatus 40 can include a cam, as shown, or other member to impart the force to the conveyor belt 20 to cause same to reciprocate. Such displacement prevents the products 22 from adhering to each other and the belt 20 during the freezing process in the space 14.

For example, IQF agitation of the conveyor belt 20 can be used in combination with the cryogen impingement jet 36 being introduced through the upper impingement plate 28 to contact the product 22. Another embodiment calls for the IQF agitation of the belt 20 to be used in combination with the upper and lower impingement plates 28,32. The lower impingement plate 32 can be used with the impingement jet 38 contacting the product 22.

Carbon dioxide (CO₂) or nitrogen (N₂) can be used as the cryogen for the jets 36,38 of the present embodiments. If liquid nitrogen is used as the cryogen, the impingement jets 36,38 will take the form of cryogen sprays, while using CO₂ as the cryogen will provide for a solid phase CO₂ in the impingement jets for contacting the products 22. Use of the liquid nitrogen can bring a temperature of the space 14 down to minus 250° F. (−156° C.), while use of CO₂ in the space can bring the temperature of the space down to minus 90° F. (−68° C.). The IQF agitation exposes 100% of the surface area of the products 22. The products 22 can be food products, such as for example shrimp, fish pieces, cutlets, fruits, vegetables, etc.

Lab testing has shown that the embodiments of the present invention will more than double the effective heat transfer coefficient that may be obtained in certain types of known mechanical or cryogen freezers. For example, known impingement freezers provide a heat transfer coefficient of approximately 18 Btu/hr*ft2*F, while known agitation or vibration freezers provide a heat transfer coefficient of approximately 12-12 ½ Btu/hr*ft2*F. In contrast, the freezer apparatus of the present embodiments provides a heat transfer coefficient of 25 Btu/hr*ft2*F, the particulars of which are shown in the following Example.

EXAMPLE

Testing of the apparatus embodiment 10 having the impingement plates 28,32 and the agitation conveyor belt 20 are as follows.

INPUTS: Equipment: Freezer Apparatus (10) Product: Fish, Shrimp Product dimension along length: 1.97 in. Product dimension along width: 0.59 in. Product thickness: 0.59 in. Space between rows: 0.1 in. Space between product pieces: 0.1 in. Number of items in row: 52 Product surface area: 5.34 in.² Piece weight: 0.021 lb. Product inlet temp: 50° F. Product outlet temp: −15° F. Freezer Details Zone 1 (inlet) SP Temperature: −70° F. Active Length of Freezer: 10 ft. Freezer Belt Width: 38 in. RESULTS: Heat Removal Results Predicted Heat Removal: 149.5 Btu/lb Actual Heat Removal: 148.8 Btu/lb Freezer Operational Inlet Data Outlet Temperature −70 −65 −60 −55° F. Gradient: Heat Transfer 25.0 25.0 25.0 25.0 Btu/hr*ft2*F. Coefficients: Product 30.8 28.3 15.4 −13.8° F. Temperatures: Retention Time: 2.37 min. Belt Loading: 2.1 lb/ft2 Heat Transfer Coefficient: 25 Btu/hr*ft2*F.

The freezer embodiments discussed above increase, and in certain instances as much as double, the overall heat transfer coefficient of a conventional cryogen freezer. Accordingly, because of the increased heat transfer rate of the present freezer embodiments, such embodiments can be constructed of a shorter length and smaller footprint than known cryogen freezers, yet still provide the same production rate and efficiency for the products being frozen. This provides a cost savings for the equipment without sacrificing the fast rate of time that the products are frozen which also results in a higher quality frozen product.

It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result. 

What is claimed is:
 1. A freezer for a product, comprising: a housing having a space therein, and an inlet and an outlet in communication with the space; a conveyor having a first side for conveying the product through the space, and a second side opposite to the first side; an agitating apparatus disposed proximate the conveyor for contacting the conveyor at select intervals to agitate the conveyor and displace the product at the first side; a first longitudinal member disposed proximate the first side of the conveyor and having at least one hole extending therethrough; and at least one circulation device disposed in the space proximate the longitudinal member for directing a cryogenic substance through the at least one hole onto the product.
 2. The freezer of claim 1, wherein the at least one hole is in registration with the conveyor.
 3. The freezer of claim 1, wherein the first longitudinal member comprises a first plate having a plurality of the holes therethrough.
 4. The freezer of claim 1, wherein the at least one hole has a diameter of 6 mm to 50 mm.
 5. The freezer of claim 1, wherein the cryogenic substance is selected from the group consisting of carbon dioxide (CO₂) and nitrogen (N₂).
 6. The freezer of claim 1, wherein the conveyor comprises a mesh surface area through which the cryogenic substance can pass.
 7. The freezer of claim 1, further comprising a second longitudinal member disposed proximate the second side of the conveyor and having at least another one hole extending therethrough.
 8. The freezer of claim 7, wherein the at least another one hole is in registration with the conveyor.
 9. The freezer of claim 7, wherein the second longitudinal member comprises a second plate having a plurality of the holes therethrough.
 10. The freezer of claim 7, wherein the at least another one hole has a diameter of 6 mm to 50 mm.
 11. The freezer of claim 7, wherein the cryogenic substance is selected from the group consisting of carbon dioxide (CO₂) and nitrogen (N₂).
 12. The freezer of claim 7, wherein the conveyor comprises a mesh surface area through which the cryogenic substance can pass.
 13. The freezer of claim 1, wherein the agitating apparatus is disposed proximate the second side of the conveyor.
 14. The freezer of claim 13, wherein the agitating apparatus comprises a cam.
 15. The freezer of claim 1, wherein the product comprises a food product. 